1. Field of the Invention:
The invention relates to an apparatus for the controlled removal of flowable bulk material at the underside of a bulk-material column located in a container, in as parallel a plane as possible, especially with a migrating-bed filter for eliminating used filter material in the course of scrubbing gaseous or vaporous media, the filter material or bulk-material column having a flow of such media therethrough from bottom to top in a direction opposite to the direction of flow of the bulk material.
2. Description of the Related Art:
A particular problem in an apparatus of this generic type is how to remove the bulk material or filter material in a plane-parallel manner, without forming preferential flow zones for the gases or vapors flowing in at the bottom that create hollow spaces in the lower area of the bulk-material column or migrating-bed filter. A further problem is how to construct the apparatus so that a metered trickling-down process which acts as a reciprocating or piston flow, causes the plane-parallel removal of the filter material, without jamming throughput adjusting devices on the underside of the column and without requiring special and costly provisions for sealing.
Migrating-bed filters for cleaning gaseous or vaporous media, to which the invention preferably relates, are more particularly adsorption filters, in the form of so-called activated carbon filters, which play a particularly important role in the decontamination of exhaust air in nuclear engineering facilities, such as nuclear research laboratories or nuclear power plants. For example, reference should be made to German Patent No. DE-PS 26 25 275. The most important goal is to filter out radioactive iodine and to remove gaseous hydrocarbons from the air exhausted from buildings; the activated carbon filters cooperate with high-efficiency submicron particulate filters. In activated carbon filters, the bulk-material column is in the form of the filter bed of the activated carbon bodies. For instance, these may be cylindrical bodies from 1 to 2 mm in diameter and 1.2 to 2 mm in length which are made from extruded coal, or they may be in the form of "broken particles" having a particle size of from 1 to 2 mm. The activated carbon filters are also known as iodine sorption filters of the migrating-bed filter type. German Published, Non-Prosecuted Application No. DE-OS 34 06 413 describes an apparatus of this generic type, with which an attempt has been made to address the above-described problem; however, it has been found that the pyramid-shaped flow guide devices therein, which have lateral surfaces ending in gutter-like trickle-down openings at the bottom of the bulk-material column, do not permit a homogenous bottom to top flow of the gases or vapors that are to be cleaned through the column. It has also been found that because of the grating thereof which is moved back and forth along with its deposits of bulk material located in chambers in the grating, the activated carbon undergoes additional shear stress in the vicinity of the trickle-down openings.
These disadvantages also arise in an apparatus described in Netherlands Published, Prosecuted Application No. 99 697.